The process in which an individuated expression of spirit is reborn into a succession of lives. The strive towards perfection requires the descent into the world of matter, in order to gain experience not obtainable in other planes of existence. Reincarnation is controlled by the operation of the natural law .
A Buddhist theory suggests that reincarnation cycles are growth oriented that have their roots in the human plane of existence by initiating into this life form which may be mentally deficient, retarded, or of a third world environment where simplicity is the norm. Subsequent earthly sojourns create a conformist state of being where virtually all is accepted by society and religious people. The next state is an independent state, where the individual questions societal norms and religious dogma and seeks to understand concepts in a more metaphysical sense. The final state is a spiritual state, depicted by such individuals as Buddha, Jesus, Lao Tze, Ta Mo, Mohammed, etc. These spiritual state teacher /masters embrace the metaphysical context and endure the final process of separating themselves from all ego-conscious and external desires.
In general, life is a classroom in which there are lessons to learn. If we fail to learn these lessons, we have to return to it to do so. There is no set period of earthly time that dictates when an individual will return. It is governed by circumstance and a plan that exists for them to do so.
Where reincarnation occurs, it can be that what is incarnated is another fragment of that individuality (group soul) which attains the necessary experience through earthly life to help in the unfoldment of the larger individuality of which it is a part. Reincarnation is not so much a voluntary act, but a sense of purpose. Nobody orders us to reincarnate into this world. We feel we have a lesson to learn, a service to perform, a wrong to redress, a kindness to be done that had failed before. We want to reincarnate because we know it is best to do so.
There are conflicting accounts of whether affinities of the same soul (essence) incarnate at the same time on earth. There is also contrasting views as to whether complete harmony occurs between them.
An individual can reincarnate and have many personalities. Personalities are not repeated. These are the physical expressions, manifestations of the individuality, but the individuality is unchanged. Reincarnation is a complex subject and not easy to explain within any earthly language.
According to Seth, each of us experiences a group of simultaneous physical lives during various historical periods--past, present and future. Each incarnation is one essence of the group soul or entity. The choice of culture and expression may be guided by the psychic family a soul belongs to. But ultimately, the soul will choose that country, or race, or sex, which is necessary for its new unfoldment.
An individual ceases to reincarnate into this world when there is no Karmic debt to pay and no service to give. With their earthly task completed, they can continue to progress in higher planes or in the world of spirit.
However, those who accept reincarnation tend to think of such lives as following one after another. While we dwell in time and space it is easier to accept conventional reincarnation, but once we escape the confines of time and space, the simultaneous physical lives description is quite logical. Once outside of the space-time structure, a primitive soul can be planted ahead in linear time of a more evolved soul. A variation on this theory is that there are counterparts of one's higher self animating life in this and other spheres simultaneously.
Evidence of reincarnation is accepted when the consciousness is ready. Even when the soul knows, it may not be able to express itself of this knowledge through the mind.